CA2078425A1 - Resins with reduced epichlorohydrin hydrolyzates - Google Patents

Abstract

RESINS WITH REDUCED
EPICHLOROHYDRIN HYDROLYZATES

ABSTRACT OF THE DISCLOSURE
Polyamidoamine-epichlorohydrin resin solutions with less than 1500 ppm of epichlorohydrin hydrolyzates after acid stabilization are produced by contacing the resin solution with either (a) dibasic phosphate salts having the general formula M2HPO4 where M represents Na, K, or NH4, or (b) a nucleophilic alkanolamine at a temperature of less than about 50° C for a time sufficient to produce a product solution having, after stabilization with acid, less than 1500 ppm of epichlorohydrin hydrolyzates.
Atty. Dkt. No. 36309 14

Description

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RE~INS WlT~ R~UC~D
E~C~OROHYDRIN EYDROLYZATES

F~LD OF ~E INVENIION
S The invention relates to a process for rnal~ng polyamidoamine epichlorohydrin resln products having a low level of residual epichlorohydrin hydrolyzates, D~SCR~ON QF R1~LAI~D 1~0I,O~Y
Polyamidoamine epichlorohydrin resin products e~hibiting thennoset properties are useful for increasing the wet strength of papers and reducing paper "creep" while the paper is wet. As such, these resin products are in wide use and in contact with consumers on a daily basis.
Polyarnidoamine epichlorohydrin resins can be made by the r~don of epichlorohydrin with a polyamidoarnine under basic conditions (i.e., a pH betPveen about 7 to absut 11). The resulting resin is then contacted with an a~'id to stabilize the producL
See, U.S. Patent Nos. 3,311,594 and 3,442,754. Any unreacted epichlorohydrin in the product is hydrolyzed by the acid to, inter a~a, 1,3~ichloro-2-propanol (l,~DCP), 3-chloro-1,2-propanediol (CPD), and 2,3-dichloro-1-propanol (2,3-DCP). Ihe 1,3-DCPproduct is the predominant hydrolysis product vith CPD being fonned in levels of a~out 10% of the 1,3-DCP and 2,3-DCP being formed in levels of about 1% of the 1,3-DCP.
Although the final product will contain æveral other types of organic chlorines (as measured by the difference between inorganic chloride and total chlorine concentrations), the 1 ,3-DCP and CPD concentrations can be accurately determined by C13 NMR and GC-MS measuring techniques known in the art. The 2,3-DCP concentrations are, however, generally below the detection limit of C13 N~ so 1,3-DCP and CPD are generally used as measurements ~or the epichlorohydrin hydrolysis products present in the resin.
Epichlorohydrin has recen~y been classified as a potential human carcinogen and there is some concern that the hydrolysis products therefrom may pose similar health concerns. There is also some indication that the organic chloride hydrolyzates contribute to adsorbable organic halide contamination of eMuent waters. It is, therefore, desirable A~. Dk~ NO. 36309 ` 2 ~ 7 8 d 2 .
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to develop wet strength resins ha~ing low levels of epichlorohydrin and its hydrolysis products. 'rhere is some indication, though that elimination of all hydrolyzate~ may adversely affe~t product pe~fo~nance because hydrolyzates con~ibute to the ability of the resin product to provide wet strength for pap~r products. See, column 2 of IJ.S. Patent No. 4,853,431.
A number of recent publications address the problems of residual hydrolyzates for polyamidoarnine epichlorohydrin resin produets.
U.S. Patent No. 4,975,499 describes an object of the invention as producing a crosslinkable polyamidoamine resin comparable to the conventional epichlorohydrin resins in wet strength effect but with less organically bound halogen. The manufac~ring process includes the reaction of dicar'ooxylic acid with particular polyamines to make the polyamidoamine which is then reacted with the epichlorohydrin and a base at a pH of 8-14 and a temperature of 15-95 C. Useful bases include lithium hydro~ide, alkaline earlh hydroxides, ammonia, sodium or potassium ~ubonate, and sodium or potassium phosphate.
Halogen-free acids are then added to end the reaction and stabilize ~e soluhon. Ihe examples report resins having org~ic chloride contents within the range of 0.11~.16%
(11001600 ppm).
U.S. Patent No. 5,017,642 describes the formation of polyamidoamine-epichlorohydrin resins having low levels of organic chloAde compounds. The manufacturing process involves control over the molar ratio of epihalohydrin to the secondary amine of the polyamidoamine. At reaction temperatures within the range of 10-45 C, this molar ratio is 0.85-1.4. At temperatures in the range of 45-55 C, the ratio is 0.85-1.25. A holding step at 25-70C is used until the viscosity of a 15% solution falls within the range of 10-100 cps. Thereafter, acid is added to stabili7e the polymer. The resins of the exarnples have dichlorohydrin concentrations within the range from 100 ppm to 16,800 ppm. Total organic chloride concentrations were not reported.
U.S. Patent No. S,019,606 also relates to the manufacture of polyamidoamines to produce resins having less than 4% of organically bound chlorine. The process involves reacting the polyamidoamine with epichlorohydrin in the ratio of 0.~2 moles epichlorohydrin per mole of basic amino groups in the polyamidoamine. The resin solution Any. Dkt. No. 36309 2 2 ~ 7 ~

is then react~d with 0.1-1 mole of base pe~ mole of e~ichlo~ohydri~ at 25-95 C(preferably 40-70 C) and a pH of greater ~an 8 (pre~erably between 9-12). lbe solution is then re-acidified by the addition of acid to a pH of 7 or les~ (~referably l.S-S~. The bases disclosed as useful for the treatment are ~i me~al hydroxides, alkaline earth metal S hydroxides, carbonates, bicarbonates, benzyltrimethylammonium hydro~cide, te~ramcthylammonium hydro~cide, tetraethylammonium hy~ro~ide, and mLl~tures thereof.
One method for controlling the epichlorohydrin residue concentrations is to control the reactant ratios during the process of malcing the resin. Reducing the amount of unreacted epichlorohydrin is useful to some e~tent because unreacted epichlorohydrin in the 10 resin will hydrolyze when the stabilization acid is added to the resin and increase the 1,3-DCP and CPD levels in the product. Manufacturing cont~ls can only go so far, however, toward solving the problem of epichlorohydrin hydrolyzates in the final, stabilized resin product. ~ydrolyzates continue to be formed inherently during the polyamidoasnine/e~ichlorohydrin polymenzation reaction.
There exists a humanitarian and commercial need for a process for reducing the amount of epichlorohydrin hydrolyzate mate~ials in e~cisting polyamidoarnine epichlorohydrin resin products as well as future products. It would also be desi~able to have a process for reducing the total amount of organic chlorine in the resin products as a safeguard that such materials might be later found to pose an environmental or health 20 risk. Preferably, such a process would not substantially affect the efficacy of the resin product in providing wet strength to paper or creping.
Sl11~Y OF TEIE ~ mON
It is an object of the invention to provide a process for making acid-stabili~edpolyamidoan~Lne epichlorohydrin resin products that exhibit low levels, e.g., less than about 1500 ppm, of 1,3-DCP and CPD.
It is also an object of the invention to provide a process for reducing the total amount of organic chlorine in acid-stabilized polyamidoamine epichlorohydrin resin products.

Atty. Dkt. No. 36309 3 ~ 2 ~ ~ 8 ~

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In accordance with these and other oSjec~ve~ of ~e invention that will become apparent from thc ~iption oontain~d her~in, pr~ces~es according to the ~nventioncompris~:
contacting an aqueous solution oomplising polyamide epichlorohydrin resin and S greater than 1500 ppm of e~ichlorohydrin and its hydrolyzate~ with a nucleophile selecled from the group oonsisting of: (a) dibasic phosphate salt~ having the general fonnula M2HPO4 where M represents Na, K, or N~,; and (b) a nucleo~hilic alkanolamine, wherein the contacting occurs in a reaction solution having a pH within the range ~om about 8 to less than 11 at a temperature of less than about 50 C and for a time sufficl~nt that, aher 10 contact with a stabilizing amount of an acid, the resin product has less than 1500 ~pm of 1,3 dichloro 2-propanol and 3-chlor~1,2-propanediol. Preferably, this reduction in 1,3-DCP and CPD will be accomp~nied by a reduction of at least 60% in ~e amount of organic chlorine in the stabilized product compared to the resin solution before ~act with the nucleaphile.
The process may be used for resîns that have been p~iously stabilized wi~ acid by adding a base, treating the resin, and then adding additional acid to ~ t~ resin.
Alte~natively, the treatment may be integrated into a continuous resin manufa~g process to include eontact with nucleophiles according to the invention aRer resin formation but before any stabilization acid has been employed. Processes of the inven~on pro~ride 20 resin products that e~hibit significantly lower amounts of 1,3-DCP, CPD, and organic chlorine than those of previous processes without significant sacrifice in the ability of the product to impart wet strength to paper products.
D~TAILED DEscR~ oN
The invention involves contacting polyamidoamine epichlorohydrin resin products 25 containing unreacted epichlorohydrin and epichlorohydrin hydrolyzates with a nucleophilic agent under controlled pH and temperature to preferentially attack the epichlorohydrin and its hydrolyzates without gelling the resin or denatuIing the product polymer. The nucleophile displaces the chloride on the epichlorohydrin and hydrolyzate mole ules and removes them from the acid-base equilibrium process without changing the polyamidoamine Atq. D~t. No. 36309 4 ~ 2073~2~
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epichlorohydrin polymer or significantly affecting its abiliq to pro~ide wet ~ength in P~-Processes for mal~ng polyamidoamine epichlor~hydrin resins are well Imown from, inter alia, U.S. Patent Nos. 2,926,154, 4~853,431, and S,019,606 which are herein S incorporated by referenoe. Briefly describ~, these proce~ occur in two ~teps: the first ste~ comprises fom~ing a polyamide by reacting a ~o~cylic acid, dicarbo~ylic acid halide, or diester with a polyalkylene polyamine at a tempe~re within the range of 40 -250 C. The polyarnide is then reacted with e~ichlorohydrin under basic conditions and a temperature within the range of 45-100 C for 3~ hours to form an aqueous solution of the polyamido~nine epichlorohydrin resin at a solids concen~ation within the range of about 5~0%. Tbe final product is made by adding at least one acid ~at will change the pH generally to wi~in the range of about 3 to less than 6.
Epichlorohydrin polyan~idoan~ine resin p~oduct solutions are typically rnade acidic to pro~ride long term storage stability to the solution. Plefe~ed acids for stabiliza~on include sulfuric acid, fonnic acid, nitric acid, acetic acid, p~o~pho~ic a~id, hydrochloric acid, phosphoric acid, phosphorous acid, and hyp~phosphorous acid~.
The resin products that can be treated in the present invention may be in th~ form of an e~isting acid-stabilized product or may represent a basic resin solution before acid stabilization. If in the fonn of an acid-stabilized resin product, the product must be neu~alized by the addition of a strong base to make the resin soludon ~eacti~e. Resin solutions that are already basic or neutral need no further treatment to be used in the present process. ll~e present process is weU suited as an au~ciliary step in conventional polyamidoamine epichlorohydnn resin manufacture just before the stabilizadon acid is conventionaUy added to the resin solution.
Nucleophilic bases suitable for removing epichlorohydrin hydrolyzates include: (a) dibasic phosphate salts haYing the general formula M2HPO, where M is Na, K, or NH~;
and (b) alkanolamines having one to eight carbon atoms, preferably two to SL~ carbon atoms. Alkanolamines useful for the present process preferably have low volatili~ to avoid noxious odors and volatile organic emissions in the final product although volatile nucleophilic alkanolamines can be used if odors are not a problem or can be removed prior Att~. Dld. No. 36309 5 ~J w 2 ~ 2 ~J~

to use. Preferred nonvola~le all~anolamine~ include monoethanolamine, diethanolamine, triethanol~rline, 2-dimethylaminoethanol, and aminopropyl diethanolaminc.
Diethanolamine ;~ the most p~eferred nucleo p~ilic base for use in the p~sent process.
The nucleophilic base conce~l~tion used in the present process should be selected 5 to ~void gelation (at lowe~ concenhation~) to an economically useful levd for the amount of e~ichlorohydrin and hydroly~te re~ in the product. Gener~lly, ~e number of moles of nucleophilic base concentration is selected to be approximately the same as the combined number of moles of epichlorohydrin (if any is present) and its hydrolyzates in the polyamidoan~ine epichlsrohydrin resin ~eing ~reated, i.e., about a 1:1 molar ra~o of 10 nucleophile to epichlorohydrin plus hydrolyzates. If the molar concentrations are converted to weight ratios, useful nucleophilic base conc~trations are usually within the range &om about 0.1% to about 596, preferably 0.75% to about 2%, and more preferably 1-2% by weight based on the weight of the epichlorohydrin polyamid~e resin solu~on. i Removal of hydrolyzates ui~ a nucle~philic am1ne or dibasic salt ~hould not be 15 confused with merely adding a base to shifi equilibnum concen~ations, e.g., NaOH merely shifts the dichloropropanol/epichlorohydrin equih'brium. Suitable nucleophilic amines according to the invention remove organic chlonnes from the reaction.
The pH, temperature, and time for the nucleophile contacting step are chosen to reduce the organic chlorine levels in the acid-slabilized prvduct by at le~st 60%, preferably 20 at least 70%, and even more preferably at least 80%. These reduction levels should coincide with a final level of 1,3-DCP and CPD in the acid-stabilized product that is less than 1500 ppm, preferably less than 1250 ppm, and even more preferably less than 1000 ppm.
The pH of the combined polyamidoan~ine epichlorohydrin resin and nucleophilic 25 alkanolamine should be maintained within the range from about 8 to about 11, preferably within the range from a~out 9.5 to less than 11, and most preferably within the range from about 10 to about 10.5. Operating below the suggeste~ range can be performed although the reaction between the epichlorohydrin hydrolyzate and the aLkanolamine may be slower than economic for many manufacturing facilities. Operating at a pH of higher than about 30 11 can denature the polymer. The basic pH of the solution is maintained by adding a base Atty. Dkt. No. 36309 6 ~J 2 ~

as needed. Suitable base3 for ~ntrolling the solu~on p~I include sodium hydro~ide, potassium hydro~ide, and sodium carbonate..
The tempe~e sf the oom~ d polyamidoQn~ine epichlorohydriD re~in and nucleophile should be maintained at less than 50 C to avoid denaturing the polymer and S below about 20 C to avoid long rea~ mes. Prefared temperature~ of the re~
nucleophile ~olu~ within ~e ange from about 20 C ~ about 40 C. Most preferredtemperatures are within the range from about 25-30C.
The epichlorohydrin polyamidoa;nine resin should be allowed to react wîth the nucleophile for as long as necessa~y to reduoe the epichlom~ydrin hydr~lyzate and organic 10 chlorine concentrations to as low as possible in the acid-stabilized product. aenerally, a contac~ng time within the range from about 4 to about 8 hours will b¢ sufficient depending on the alkanolamine, pH, and contact temperature although longer pe~iods may be used if necessary. ~lth tbe preferred embodirnent of the inventio~, a wntact time of about 6 hours is usually sufflcient~
The 1 ,3-DCP and CPD concentrations in the acid-stabilizod ~sin are convenien~y detern~ined using the know,n technique of C~ N~ with a dimetJiyl sulfo~ide (I)MSO) calibration standard. The ratio of 1,3~ichloropr~panol to DMSO is linear with respect to the DMSO concentration and can be used to generate a calibration curve to the hydrolyzate concentration for the particular measuring apparatus. The concentration of 2,3-DCP is 20 generally below the detection limits of C13 NMR and does not generally enter into the measurement of hydrolyzate concentration in the acid-stabilized product. The C13 NMR
method is non-invasive and does not rely on extraction--a m~thod which can affect the accuracy of a concentration analysis because the epichlorohydrinJhydrolyzate equilibrium shifts during the e~t~action process.

E~arnple 1 TO 3502.9 g of a commercially available epichlorohydrin polyamidoamine resin solution (22~o) containing about 0.80% total organic chlorine and 0.62% of 1,3-DCP and CPD combined at a pH of about 7 was added 66.12 g of an 85 % solution of 30 diethanolamine. The pH of the reaction mL~ture was held constant at 9.3 for four hours Atty. Dkt. No. 36309 7 by the intennittent addition of a 50% NaOH solution. Ibe ~emperatu~e was held constant at 35 C. The pH was then adjust~d to 3.0 by the addition of 134.9 g of 35% aqueow sulfuric acid. Ibe ~olids content of the resin solution wa~ adjusted to 12.5% by ~e addi~on of 766.7 g of water. The product resin e~hibited about 0.1S% of total organic S chlorine and 0.07% of the o~mbined weights of 1,3-D~ and CPD based on ~e weight of the resin solid3.
Organic chlorine was reduced by about 81% and the e~ichlorohydrin hydroly~ate concentration was reduced by about 89%.
E~ample ~
To 500 g of a commercially available epichlorohydrin polyamido~ resin solution (25%) containing about 1.77% total organic chlo~ine and 2.1% of 1,3-DCP and CPD combined at a pH of about 7 was added 13.75 g of diethanolamine. The system pH
was maintained within the range of 9.1 to 9.3 by the ~ddition of 50% NaOH for seven hours. Sulfuric acid was added in an amount sufficient to reduce the solution pH ts 3.1S.
The acid-stabilized resin solution exhibited an organic chlo~ne content of 0.70% and 0.35% of the combined weight3 of 1,3-DCP and CPD basod on the weight of the resin solids.
Organic chlorine was reduced by about 60.5% and the epichlorohydrin hydrolyzate concentration was reduced by about 83%.
Example 3 Example 2 was repeated except that: (a) the star~ng organic chloride content was1.80% and the combined weights of 1,3-DCP and CPD were 3.3%; ~b) the pH was maintained within the range of 9.3 to 9.5; and (c) and the contacting was permitted for only 6 hours. Sulfuric acid was added in an amount sufficient to reduce the solution pH to 3.08.
The final organic chlorine content was 0.57% and the combined weights of 1,3-DCP and CPD were 1%.
Organic chlorine was reduced by about 68% and the epichlorohydrin hydrolyzate concentration was reduced by about 70%.

Atty. Dl~ No. 36309 8 ~, ~ 2~7~2~

nplcs 4-9 ~amples 4-9 followed ~e same fundamental p~ooedure a~ e~am~a 1-3 using a 12.5-13 % solids e~ichlorohydrin polyamidoamineresin solu~on. The final o~ganic chlonne content (RCI) was measured after addition of a stabilizing arnount of sulfuric acid (ex. 4-8) 5 or phosphoric acid (e~. 9).
E~ample ¦ Nucl~ Du~a~ion ~1~;~ X
I l (start) (ald) drop -~ ...... _ , _,.. ___. __ ~ ..... _ 4 DEA 9.1-9.7 3 hrs 40 mins. O.W%0.20 75%

9.2-9.5 4 ~ 10 ~ins. Oab0%0.25 69%

6 9.2-9.5 3 hrs 37 mins. 0.80% O 19 76%

7 APD~A 9.2-9.5 3 hr~ about0.21 74X
8 DEA 9.2-9.5 41~ abouto.æ 73 X
....
9 DI~A 9.2-9.5 4 hrs 0.80X0 20 75 DI~A = diethsnolaminc l~A = ~iethanolam~
MEA = mo~oethanol~miDe APDl~ = aminopropyl dielhanolami~:

E3cample 10 Nucleophilic amines were compared with nucleophilic dibasic phosphate salts for 20 their effects on reducing the organic chlorine contents in 50 g off a conventional epichlorohydrin polyamidoan~ne resins having 12.5% solids. The solution was held at 25 C and replicate samples were made at a pH of 8 and a pH of 10 adding sulfuric acid or sodium hydro~ide as needed to overcome the initial buffering effects of ~e nucleophiles although the amount of each nucleophile used at the pH of 8 was the same as the amount 25 used at a pH of 10. The pH of each solution was not otherwise controlled during the . An~. Dkt. No. 36309 9 2 ~ 7 ~

reaction. The treatrnent was allowed to con~nuc f~r ab~ut 16 hou~ before adding stabilizing amount~ of 3S% sulfuric ~d.
I 7~ __ E~. ¦ Nucleophile pH RCI % RCI X ~ Drop l (gta~t) (end) ~ __ _~ __ __ S10 TB~ 8 0.80 0.69 14 _ _ __ ~
11 TEA 10 0.80 0.43 46 _ _ _ __ .
12 ~C~HPO" 8 0.80 0_60 13 K2HPO~ 10 0.80 __ 0.26 68 14 (NH~)2~4 8 0.80 0.65 19 ~ ... _ _ l 15 (NH~)2HPO~10 0.80 gd 16 DEA 10 0.80 0.27 66 ., . ~ .. , "". ~ ,_ It should be noted that the ammonium phos~ of example~ 14 and lS did not perfonn as well a~ e~pected in the prccess. The reduced efficacy is ~ought to b rda~l 15 to the lack of con~ol over the solution pH during the ~ on of ~e dibasic pho~ate salt with the organic chlorine compounds. Accurate control over ~e solution pH would reflect a different and more usefill result.

Att~. Dl~t. No. 36309 10

Claims (17)

1. A process for preparing a polyamide-epichlorohydrin resin solution product exhibiting low levels of epichlorohydrin hydrolyzates, said process comprising:
contacting an aqueous solution comprising epichlorohydrin polyamidoamine resin and greater than 1500 ppm combined weight of epichlorohydrin and its hydrolyzates with a nucleophile selected from the group consisting of (a) dibasic phosphate salts having the general formula M2HPO4 where M represents Na, R, or NH4, and (b) a nucleophilic alkanolamine, wherein the contacting occurs in a reaction solution having a pH within the range from about 8 to about 11 at a temperature of less than about 50° C for a time sufficient to produce a resin product solution which, after stabilization with a stabilizing amount of an acid, exhibits less than 1500 ppm of 1,3-dichloro-2-propanol and 3-chloro 1,2-propanediol.

2. A process as in claim 1 wherein the contacting step comprises contacting said aqueous solution with a nucleophilic alkanolamine in an amount within the range of 0.1% to 5 % based on the weight of said aqueous solution.

3. A process as in claim 1 wherein the contacting step comprises:
contacting said aqueous solution with a nucleophilic alkanolamine having one to eight carbon atoms.

4. A process as in claim 1 wherein the contacting step comprises:
contacting said aqueous solution with a nucleophilic alkanolamine selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, aminopropyl diethanolamine, and 2-dimethylaminoethanol.

Atty. Dkt. No. 36309 11

5. A process as in claim 1 wherein the contacting step comprises:
contacting said aqueous solution with diethanolamine.

6. A process as in claim 1 wherein the contacting step further comprises maintaining the pH of said reaction solution within the range from about 9.5 to less than 11 by adding a base.

7. A process as in claim 1 wherein the contacting step further comprises:
maintaining the pH of said reaction solution at a pH within the range from about 10 to about 10.5.

8. A process as in claim 1 wherein the contacting step comprises:
contacting said aqueous solution with said nucleophile at a temperature within the range from about 20°C to about 50°C.

9. A process as in claim 8 wherein the contacting step comprises:
contacting said aqueous solution with said nucleophile at a temperature within the range from 25°C to 35°C.

10. A process for preparing a polyamide epichlorohydrin resin solution product exhibiting low levels of organic chlorine, said process comprising:
contacting an aqueous solution comprising epichlorohydrin polyamidoamine resin and greater than 1500 ppm combined weight of organic chlorine with a nucleophile selected from the group consisting of (a) dibasic phosphate salts having the general formula M2HPO4 where M represents Na, K, or NH4, and (b) a nucleophilic alkanolamine, wherein the contacting occurs in a reaction solution having a pH within the range from about 8 to about

11 at a temperature of less than about 50° C and for a time sufficient to produce a resin product solution which, after stabilization with a stabilizing amount of an acid, exhibits at least 60% less organic chlorine than said aqueous solution before contact with said nucleophile.
Atty. Dkt. No. 36309 12 11. A process as in claim 10 wherein the contacting step comprises:
contacting said aqueous solution with a nucleophilic alkanolamine in a concentration within the range from 0.1% to 5% based on the weight of said aqueous solution.

12. A process as in claim 10 wherein contacting step comprises:
contacting said aqueous solution with a nucleophilic alkanolamine having one to eight carbon atoms.

13. A process as in claim 10 wherein the contacting step comprises:
contacting said aqueous solution with a nucleophilic alkanolamine selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, aminopropyl diethanolamine, and 2-dimethylaminoethanol.

14. A process as in claim 10 wherein the contacting step comprises:
contacing said aqueous solution with diethanolamine.

15. A process as in claim 10 wherein the contacting step further comprises:
maintaining the pH of said reaction solution within the range from about 9.5 to less than 11 by adding a base.

16. A process as in claim 10 wherein the contacting step comprises:
contacting said aqueous solution with said nucleophile at a temperature within the range from about 20°C to about 50°C.

17. A process as in claim 16 wherein the contacting step comprises:
contacting said aqueous solution with said nucleophile at a temperature within the range from 25°C to 35°C.

Atty. Dkt. No. 36309 13